I have 4 Frontosa that are about 4-5" (never really sure how you measure a fish). While I know that some recommend keeping them alone I'd like to add a few colorful fish to the tank. I do not want to mix lakes. Thank you for any suggestions.
Although Frontosa grow pretty big, they`re gentle giants and are open to being bullied which is why it`s recommended that they`re kept in a species only setup. even then, you may still find one in particular being bullied.
Tanganyikans aren`t the best fish if colour is what you`re after, unless you get some of the Jumbo cyprichromis, but you never know what species you`re actually getting unless you buy from a breeder. Plus, you`re right about not mixing the lakes so it kind of limits your stocking. I personally would just enjoy the Frontosa that you currently have and continue to keep them on their own
neolamprologus tretocephalus and sexfasciatus may be worth looking at. Both get a reasonable size (about 15cm max) and im fairly sure you can keep them with frontosas but its worth getting a second opinion on those.
Altrolamprologus compressiceps is another one of the larger tangs that is quite commonly seen. decent colours on the adults
to be honest with you, if it were my tank it would be a species only tank with more frontosas, they do so much better in a larger group!!